The percentage of the country’s public high school students who scored three or higher on AP exams continues to grow, according to results released Wednesday by the College Board. Nationally, just under 22 percent of the class of 2016 achieved a three or better mark, up slightly from 2015 and nearly eight points up from 2006.

Scores for Advanced Placement exams are on a five-point scale, with a three generally considered passing. Higher AP scores allow students to obtain college credits or skip entry-level college classes.

Massachusetts led all states with 31 percent of its students scoring three or higher. Maryland, which had held the top spot since 2008, dropped to second position with 30.4 percent of its students achieving passing grades. Connecticut (30.1), Florida (29.5) and California (28.5) rounded out the top five.

Seventeen states scored higher than the national average, including Virginia (28.3). In the District of Columbia, which is included in the results but whose test results cannot be easily compared with those of states, 13.8 percent of the class of 2016 achieved three or better on AP exams.

Last year, the District’s results were better than about half of all states’. This year, 34 states performed better than the District.

Mississippi trailed all states with just under 6 percent of its students achieving three or better. Louisiana, North Dakota, Nebraska and Kansas were among the five worst-performing states.

AP exams are offered in a wide variety of subjects, and each year, more students are taking them. In 2006, 645,000 students took at least one AP exam each. In 2016 that number had grown to 1.1 million.

College Board President David Coleman said in a conference call with reporters that while the number of students taking AP tests continues to grow, the bigger news is that performance on the tests continues to improve.

Citing research by Nat Malkus of the American Enterprise Institute, Coleman pointed to achievement gains on the AP after the tests were made available to more students.

“Most people tend to believe that if you increase access in a big way, you’re likely to compromise on quality,” Coleman said. “Against all those instincts . . . the Advanced Placement program has radically expanded access without compromising quality.”

Trevor Packer, a senior vice president at the College Board, said the research was a “landmark” finding that showed more students had the same academic ability “as the much smaller population that was getting into AP classrooms so many years ago. In other words, educators have been eradicating both the written and unwritten rules that restricted college credit opportunities to artificial thresholds like the top 10 percent of a high school.”

A significant part of the increased participation in AP testing has been by low-income students whose test fees have been paid in part with federal funds. More than 450,000 students who took AP tests in 2016 received federal funding to help pay for the exams. Under a new federal law, the Every Student Succeeds Act, the federal funding for test fees will be given to states to distribute.

That change worries Coleman, who said it has caught states and school districts off guard.

“There’s a huge danger that without dedicated resources, these participation rates shall be in danger, particularly among the most vulnerable,” Coleman said.